Probiotics are strains of yeast and bacteria that help the human body maintain optimal wellness; they aid digestion, stimulate immune function, play a role in preventing allergies, colon cancer and dermatitis, and are helpful in the treatment of intestinal conditions. In supplements, functional foods and cosmeceuticals, probiotics may be used in a number of ways. As supplements, they are sold as stand-alone products as well as blended with other ingredients, including prebiotics, for immune and digestive issues. In functional foods, probiotics are often found in yogurt and other cultured milk products, such as kefir, most commonly as the bacteria Lactobacillus (including L. acidophilus) and Bifidobacterium, as well as the yeast Saccharomyces boulardii.
Prebiotic substances, including FOS (fructooligosaccharides) and inulin, are often combined with probiotics to provide the necessary food for healthy bacteria growth. Prebiotics, particularly FOS, are also found in skin care, where they are though to help protect skin from the effects of harmful bacteria.